shutdown: add pre-shutdown pubsub channel

subiquity/server/controllers/shutdown.py

@@ -31,6 +31,7 @@ from subiquity.common.apidef import API
 from subiquity.common.types import ShutdownMode
 from subiquity.server.controller import SubiquityController
 from subiquity.server.controllers.install import ApplicationState
+from subiquity.server.types import InstallerChannels
 
 log = logging.getLogger("subiquity.server.controllers.shutdown")
 
@@ -87,9 +88,9 @@ class ShutdownController(SubiquityController):
         await self.server_reboot_event.wait()
         if self.app.interactive:
             await self.user_shutdown_event.wait()
-            self.shutdown()
+            await self.shutdown()
         elif self.app.state == ApplicationState.DONE:
-            self.shutdown()
+            await self.shutdown()
 
     @with_context()
     async def copy_logs_to_target(self, context):
@@ -127,7 +128,10 @@ class ShutdownController(SubiquityController):
             log.exception("saving journal failed")
 
     @with_context(description='mode={self.mode.name}')
-    def shutdown(self, context):
+    async def shutdown(self, context):
+        await self.app.hub.abroadcast(InstallerChannels.PRE_SHUTDOWN)
+        # As PRE_SHUTDOWN is supposed to be as close as possible to the
+        # shutdown, we probably don't want additional logic in between.
         self.shuttingdown_event.set()
         if self.opts.dry_run:
             self.app.exit()

subiquity/server/types.py

@@ -43,3 +43,7 @@ class InstallerChannels(CoreChannels):
     # models in the "install" side of the install/postinstall divide will not
     # be reconfigured.
     INSTALL_CONFIRMED = 'install-confirmed'
+    # This message is sent as late as possible, and just before shutdown.  This
+    # step is after logfiles have been copied to the system, so should be used
+    # sparingly and only as absolutely required.
+    PRE_SHUTDOWN = 'pre-shutdown'

system_setup/server/controllers/shutdown.py

@@ -49,7 +49,7 @@ class SetupShutdownController(ShutdownController):
         self.server_reboot_event.set()
 
     @with_context(description='mode={self.mode.name}')
-    def shutdown(self, context):
+    async def shutdown(self, context):
         self.shuttingdown_event.set()
         comments = ["# This file was auto generated by system-setup.",
                     "# Don't edit it. It will be overwritten at next run."]